1. Field of the Invention
The present invention generally relates to an improved aircraft load management center, and more particularly to a fast acting, hardware efficient load management center with multiple line replacement units.
2. Description of the Prior Art
Power systems in aircraft today are commonly controlled by digital data generated by on board computers in response to manually operated switches and other inputs from various transducers. Advantageously, power switching is accomplished at one or more load management centers which connect and disconnect the various loads to the appropriate power bus by means of solid state controllers. A load management center contemplated by this invention includes a number of printed circuit boards each carrying a number of solid state controllers. In the event of a malfunction of a controller or other malfunction, the load center design is such that the board which carries the malfunctioning unit can be unplugged and replaced with a properly operating board of the same type. That is, each of the boards is what is known in the aircraft power-control art as a line replaceable unit (LRU).
Data must be transmitted between the load management center and the computer rapidly. The transmission must be fault tolerant. The load management center should automatically report controller status after each control command. All this must be accomplished efficiently in terms of hardware costs, weight, and high-speed data throughput.
Prior art suggestions for aircraft load management centers include U.S. Pat. No. 3,842,249 ELECTRICAL SYSTEM WITH PROGRAMMED COMPUTER CONTROL AND MANUALLY INITIATED CONTROL MEANS. This patent discloses an automatically controlled electrical system controlling a plurality of loads in the functions of load resetting, logical control, load sequencing, overload evaluation, and load shedding with single point control. A data entry and display means provides a manual interface with the system. The system utilizes remotely controlled power switching and circuit protective devices. A general purpose computer is used to effect control functions by multiplexed control signals. The computer directs the control signals to and from the appropriate switching devices and it also provides capability to program for automatic control, sequencing and self-checkout functions.
A Westinghouse Engineer article entitled "Automatic Control of Aircraft Electrical System Reduces Wiring and Improves Reliability", discloses a distribution system which combines remote load control and indication, signal multiplexing, and programmable control logic.
A Westcon Proceedings article entitled "Airborne Display and Electric Management System", discloses a multiplexed load management center with power control and fault sensing.
These prior art approaches do not provide an implementation which is altogether satisfactory for a load management center which employs multiple line replaceable units, each carrying a number of controllers.